Nickel(II) complexes containing thiosemicarbazone and triphenylphosphine: Synthesis, spectroscopy, crystallography and catalytic activity

Four new Ni(II) complexes of the general formula [Ni(PPh3)(L)] (L = dibasic tridentate ligand derived from 4-diethylamino-salicylaldehyde and thiosemicarbazide or 4-N-substituted thiosemicarbazide) have been reported. The new complexes have been synthesized and characterized by analytical and spectroscopic (IR, electronic, 1H NMR and 31P NMR) techniques. Molecular structure of one of the complexes has been determined by X-ray crystallography. The complex, [Ni(PPh3)(L4)] (H2L4 = thiosemicarbazone prepared from 4-diethylamino-salicylaldehyde and 4-phenylthiosemicarbazide) crystallized in monoclinic space group with two molecules per unit cell and has the dimensions of a = 13.232(6) Å, b = 10.181(5) Å, c = 13.574(7) Å, α = 90°, β = 98.483(2)° and γ = 90°. Catalytic activity of the complexes has been explored for aryl–aryl coupling reaction.